The present invention is directed to a rock drill with an axially elongated shank having a chucking shank section at one end, and a drilling tip at the opposite end with helically arranged conveying grooves extending from adjacent the drilling tip towards the chucking shank section. Helically arranged lands, located between the conveying grooves, have auxiliary grooves located between guidance regions adjacent the conveying grooves.
Rock drills of the above type are used for drilling boreholes in rock, concrete, masonry and the like. Generally, the rock drills are given a rotary motion along with a percussion motion provided by a driving device. Both motions serve for producing a drilling advance. Friction developed between conventional rock drills and the rock or other material has a negative effect upon the feed or advance of the drill, since the friction consumes a large portion of the power output delivered by the driving device.
To overcome to some degree the above-mentioned friction, known rock drills generally comprise two helically arranged conveying groves with lands located between the grooves. Since such lands must have a certain width for reasons of strength, a relatively large contact surface is formed with the rock and results in a correspondingly high friction. Additionally, this friction is increased by the drilled material or drillings which penetrate between the lands and the rock in spite of the conveying groove and due to a dragging action result in an increased friction and may even lead to jamming of the rock drill.
To overcome these disadvantages, a rock drill is known from U.S. Pat. No. 2,370,706 which has two conveying grooves with an auxiliary groove formed in the land between the conveying grooves. This auxiliary groove, intended to reduce the surface of the land causing friction, has a flat and a circular segment shape. Due to the flat and circular segment shape, it is necessary to provide a large width for the land, to afford a sufficient reduction of the surface resulting in friction. The large width of the land results in the disadvantage that the width of the conveying grooves must be selected relatively small in comparison to the width of the land. The relatively small width of the conveying groove provides only a small space for conveying the drillings, whereby an output loss occurs in this known drill due to the insufficient ability to convey the drillings.
The removal of the drillings in this known rock drill is insufficient, particularly if wet rock, concrete, masonry or the like is to be drilled, or if a cooling medium is supplied to the rock drill during the drilling operation. If the drillings penetrate into the auxiliary grooves shaped to be relatively flat toward the outside surface of the drill they can cause jamming, so that the drilling operation is impaired by an additional reduction in output. Additionally, the small width of the conveying grooves causes an unsatisfactory removal of the drillings and results in frequent interruptions of the drilling operation and, as a result, with more time being consumed.